Penthos — the Greek term for mourning or compunction — occupies a singular position in the Eastern Christian ascetic tradition and, by extension, in any depth-psychological reading of that tradition. Hausherr’s 1944 monograph remains the authoritative scholarly treatment, tracing penthos from its biblical and patristic roots through the Desert Fathers, the Philokalic tradition, and Syrian mysticism. Within this corpus the term denotes neither mere sorrow nor clinical depression but a disciplined, transformative grief directed simultaneously at one’s sins and toward divine encounter. Hausherr situates penthos in careful distinction from the eight capital vices, above all from acedia and the worldly sadness (lupē) that the Fathers condemned: penthos is the fruit of grace, not its counterfeit. The doctrine is architecturally complex — encompassing causes, means, psychological effects, and eschatological terminus — and its central paradox is that mourning generates joy. Tears function sacramentally, as a ‘fifth baptism,’ purifying the intellect and opening it to divine light. The Desert tradition further personalizes penthos as an active agent — a ‘master’ that teaches the monk what he needs — while the broader Hellenic resonance of the term, visible in Nagy’s reading of Homeric kleos and penthos as complementary categories of heroic memory, reveals its wider semantic reach across antiquity.